The results are in: DART, the mission to change the path of an asteroid, has successfully achieved its objective and moved a stadium-sized space rock further than NASA originally expected.
On 27 September, the Double Asteroid Redirection Test (DART) spacecraft was deliberately smashed into the surface of the asteroid Dimorphos at more than 23,000 km/h after an 11-million-kilometre journey.
It was part of a mission by NASA and the Applied Physics Laboratory at John Hopkins University to see whether human intervention could alter the trajectory of a space objects—such as an asteroid—in case the need to protect Earth from a catastrophic collision arises in the future.
Now, NASA has confirmed the orbit of the target asteroid has been changed by the high-speed impact, marking the successful completion of the project started back in 2017.
How do we know it worked?
The US$330 million spacecraft’s impact was only expected to shift the position of Dimorphos by one millimetre, but in the scheme of its 11-hour, 55-minute orbit around the nearby asteroid Didymos, even this miniscule shift could shave over a minute from its space loop.
Prior to the impact, the mission team finalised its calculations of Dimorphos’ orbit by measuring the eclipses between the 160-metre asteroid around its 780-metre parent – each dip of light as one passes in front of the other providing calibration intervals for scientists on Earth.
That process, was repeated in the aftermath of the collision using powerful telescopes at Lowell Observatory in Arizona and the Twin Magellan Telescopes in Chile.
These calculations found a whopping 32-minute change in Dimorphos’ orbit time – 25 times greater than the mission’s 73-second benchmark.
“This result is one important step toward understanding the full effect of DART’s impact with its target asteroid” says NASA Planetary Science Division director Lori Glaze.
“As new data come in each day, astronomers will be able to better assess whether, and how, a mission like DART could be used in the future to help protect Earth from a collision with an asteroid if we ever discover one headed our way.”
What’s next for the DART mission?
While the successful change in Dimorphos’ orbit has been confirmed, the DART mission team is continuing its analysis of the impact’s aftermath.
Initial pictures captured by the Hubble Space Telescope in the first 22 hours after the impact showed the ejecta—the eruption of asteroid debris from the point-of-impact—substantially extending as light rays from the main body.
The recoil from this eruption of debris is expected to have enhanced the effect of the DART spacecraft’s collision with the asteroid, and mission scientists will switch their focus to investigating the momentum transfer from the fast-moving ship to Dimorphos.
Understanding the unique properties of Dimorphos will inform future planetary defence planning by NASA. Such characteristics may not be common to all asteroids, including ones that may one day be set on a collision course for Earth. These analyses will be further assisted by the LICIACube satellite currently in the vicinity of the impacted asteroid, as well as the European Space Agency’s upcoming Hera mission, which will conduct a larger-scale post-impact survey of the crash aftermath.
Matthew Agius is a science writer for Cosmos Magazine.
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